“In 2014, I decided it was time to stop talking about the problems facing our country and start doing something to solve them," Mills said in a statement. "I intend to finish what I started, and look forward to working for the people of the 8th District.”

Mills lost to Nolan by less than 2 points in 2014. He has been mulling a rematch for months and formed an exploratory committee last month . Nolan has been expecting the Republican to challenge him again, he told CQ Roll Call last month.

Given his narrow re-election victory, the Democratic Congressional Campaign Committee put Nolan, who first served in Congress from 1975 to 1981, into its Frontline Program for vulnerable members.

But Democrats are optimistic that a presidential year will boost Nolan's margins. The last time he ran in a presidential year, in 2012, he defeated Republican Chip Cravaack by 9 points; President Barack Obama has carried the district twice.

But Mills, whose family owns the Mills Fleet Farm farming and sporting goods retail chain with stores throughout the Midwest, will be able to fund a campaign easily and will likely enjoy greater name recognition for his second bid.